Optical lens

Abstract

The application discloses an optical lens, which comprises, along an optical axis from an object side to an imaging surface, a first group with positive refractive power, which is composed of three lenses, and sequentially comprises, from the object side to the imaging surface, a first lens with positive refractive power, a second lens with positive refractive power, and a third lens with negative refractive power; a liquid lens with refractive power, which presents different focal lengths according to different applied voltages; a second group with positive refractive power, which is composed of four lenses, and sequentially comprises, from the object side to the imaging surface, a fourth lens with positive refractive power, a fifth lens with negative refractive power, a sixth lens with negative refractive power, and a seventh lens with positive refractive power. The optical lens provided by the application has at least one or more advantages of fast automatic focusing, a large imaging surface, and high image quality.

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 lenses focus using mechanical motion. A motor drives 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 to compensate for focus shifts caused by changes in working distance. However, this mechanical focusing method suffers from slow focusing speed, the need for manual focusing, and large size, making it difficult to meet the demands of applications requiring high real-time performance. Summary of the Invention

[0004] Therefore, the object of the present invention is to provide an optical lens that has at least one or more advantages of fast autofocus, large image 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: a first group of lenses with positive optical power, consisting of three lenses, the first group including, from the object side to the imaging plane, a first lens with positive optical power, a second lens with positive optical power, and a third lens with negative optical power; a liquid lens with optical power, the liquid lens exhibiting different focal lengths depending on the applied voltage; and a second group of lenses with positive optical power, consisting of four lenses, the second group including, from the object side to the imaging plane, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with negative optical power, and a seventh lens with positive optical power.

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

[0008] In some embodiments, the object-side surface of the second lens is convex, and the image-side surface of the second lens is concave.

[0009] In some embodiments, the object-side surface of the third lens is concave, and the image-side surface of the third lens is concave.

[0010] In some embodiments, the object-side surface of the fourth lens is convex, and the image-side surface of the fourth lens is convex.

[0011] In some embodiments, the object-side surface of the fifth lens is concave, and the image-side surface of the fifth lens is convex.

[0012] In some embodiments, the object-side surface of the sixth lens is concave, and the image-side surface of the sixth lens is concave.

[0013] In some embodiments, the object-side surface of the seventh lens is convex, and the image-side surface of the seventh lens is convex.

[0014] In some embodiments, the fourth lens and the fifth lens form a cemented lens.

[0015] In some embodiments, the liquid lens is provided with an aperture.

[0016] In some embodiments, a filter and a protective glass are provided between the seventh lens and the imaging surface.

[0017] In some embodiments, the total optical length (TTL) of the optical lens satisfies: TTL < 24 mm.

[0018] In some embodiments, the maximum field of view (FOV) of the optical lens satisfies: 30° <FOV<40°。

[0019] In some embodiments, the image height IH corresponding to the maximum field of view of the optical lens satisfies: IH > 10mm.

[0020] In some embodiments, the working object distance OBJ of the optical lens satisfies: 500mm≤OBJ≤1500mm.

[0021] In some embodiments, the driving voltage U of the liquid lens satisfies: 35V <U<48V。

[0022] In some embodiments, the effective focal length fa of the first group and the effective focal length f of the optical lens satisfy: 1.5 <fa / f<2.5。

[0023] In some embodiments, the effective focal length fc of the second group and the effective focal length f of the optical lens satisfy: 0.8 <fc / f<1.5。

[0024] In some embodiments, the effective focal length fa of the first group and the effective focal length fc of the second group satisfy: 1.5 < fa / fc < 3.

[0025] In some embodiments, the object distance OBJ of the optical lens and the effective focal length f of the optical lens satisfy: 0.008 < OBJ / f < 0.04, 14.5 mm < f < 18 mm.

[0026] In some embodiments, the effective focal length f1 of the first lens and the effective focal length f of the optical lens satisfy: 1 < f1 / f < 2.

[0027] In some embodiments, the effective focal length f2 of the second lens and the effective focal length f of the optical lens satisfy: 1 < f2 / f < 2.

[0028] In some embodiments, the effective focal length f3 of the third lens and the effective focal length f of the optical lens satisfy: -1 < f3 / f < -0.5.

[0029] In some embodiments, the effective focal length f4 of the fourth lens and the effective focal length f of the optical lens satisfy: 0.1 < f4 / f < 0.4.

[0030] In some embodiments, the effective focal length f5 of the fifth lens and the effective focal length f of the optical lens satisfy: -0.7 < f5 / f < -0.2.

[0031] In some embodiments, the effective focal length f6 of the sixth lens and the effective focal length f of the optical lens satisfy: -0.8 < f6 / f < -0.2.

[0032] In some embodiments, the effective focal length f7 of the seventh lens and the effective focal length f of the optical lens satisfy: 0.5 < f7 / f < 1.

[0033] In some embodiments, the effective focal length f1 of the first lens and the effective focal length f7 of the seventh lens satisfy: 1.5 < f1 / f7 < 2; the effective aperture DM11 of the object side of the first lens and the effective aperture DM72 of the image side of the seventh lens satisfy: 0.8 < DM11 / DM72 < 1.2.

[0034] In some embodiments, the combined focal length f45 of the fourth lens and the fifth lens and the effective focal length f of the optical lens satisfy: 0.5 < f45 / f < 1; the effective focal length f4 of the fourth lens and the effective focal length f5 of the fifth lens satisfy: -0.8 < f4 / f5 < -0.2.

[0035] In some embodiments, the effective focal length f2 of the second lens and the effective focal length f3 of the third lens satisfy: -2.5 <f2 / f3<-1.5。

[0036] In some embodiments, the effective focal length f6 of the sixth lens and the effective focal length f7 of the seventh lens satisfy: -1 <f6 / f7<-0.5。

[0037] In some embodiments, the total optical length (TTL) of the optical lens and the effective focal length (f) of the optical lens satisfy: 1.3 <TTL / f<1.7。

[0038] In some embodiments, the image height IH corresponding to the maximum field of view of the optical lens and the effective focal length f of the optical lens satisfy: 0.6 <IH / f<0.8。

[0039] In some embodiments, the radius of curvature R3 of the object-side surface of the second lens and the radius of curvature R4 of the image-side surface of the second lens satisfy: 0.3 <R3 / R4<0.6。

[0040] In some embodiments, the radius of curvature R5 of the object-side surface of the third lens and the radius of curvature R6 of the image-side surface of the third lens satisfy: -10 <R5 / R6<-2。

[0041] In some embodiments, the radius of curvature R13 of the object-side surface of the fourth lens and the radius of curvature R15 of the image-side surface of the fifth lens satisfy: -6 <R13 / R15<-1。

[0042] In some embodiments, the radius of curvature R16 of the object-side surface of the sixth lens and the radius of curvature R17 of the image-side surface of the sixth lens satisfy: -0.35 <R16 / R17<-0.1。

[0043] Compared with the prior art, the optical lens provided by the present invention adopts a combination of seven lens elements and one liquid lens element. By rationally allocating the focal length relationship between the liquid lens element and its front and rear groups, and by controlling the driving voltage of the liquid lens element to adjust the focus position of the entire optical system in real time, the purpose of fast focusing at different working distances can be achieved, and the optical lens can have high resolution at different object distances. Attached Figure Description

[0044] 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:

[0045] Figure 1 This is a schematic diagram of the structure of an optical lens provided in the first embodiment of the present invention;

[0046] Figure 2A transverse chromatic aberration curve of an optical lens provided in the first embodiment of the present invention;

[0047] Figure 3 A relative illumination curve of an optical lens provided in the first embodiment of the present invention;

[0048] Figure 4 The MTF curve of the optical lens provided in the first embodiment of the present invention;

[0049] Figure 5 A transverse chromatic aberration curve of an optical lens provided in the second embodiment of the present invention;

[0050] Figure 6 A relative illumination curve of an optical lens provided in the second embodiment of the present invention;

[0051] Figure 7 The MTF curve of the optical lens provided in the second embodiment of the present invention;

[0052] Figure 8 A transverse chromatic aberration curve of an optical lens provided in the third embodiment of the present invention;

[0053] Figure 9 A relative illumination curve of an optical lens provided in the third embodiment of the present invention;

[0054] Figure 10 MTF curve of the optical lens provided in the third embodiment of the present invention;

[0055] Figure 11 This is a schematic diagram of the structure of the liquid lens in the optical lens provided by the present invention. Detailed Implementation

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The present invention proposes an optical lens, which comprises, along the optical axis from the object side to the imaging plane, the following components in sequence: a first group, a liquid lens, and a second group.

[0064] The first group has positive optical power and consists of three lenses. Along the optical axis from the object side to the imaging plane, the first group includes a first lens, a second lens, and a third lens in sequence. The liquid lens can exhibit different focal lengths depending on the applied voltage, and an aperture stop is provided within the liquid lens. The second group has positive optical power and consists of four lenses. Along the optical axis from the object side to the imaging plane, the second group includes a fourth lens, a fifth lens, a sixth lens, and a seventh lens in sequence.

[0065] Specifically, the first lens has positive optical power, and both its object-side and image-side surfaces are convex; the second lens has positive optical power, and both its object-side and image-side surfaces are concave; the third lens has negative optical power, and both its object-side and image-side surfaces are concave; the fourth lens has positive optical power, and both its object-side and image-side surfaces are convex; the fifth lens has negative optical power, and both its object-side and image-side surfaces are concave; the sixth lens has negative optical power, and both its object-side and image-side surfaces are concave; the seventh lens has positive optical power, and both its object-side and image-side surfaces are convex.

[0066] In some embodiments, the fourth lens and the fifth lens form a cemented lens to share the chromatic aberration correction of the optical lens, improve the resolution of the optical lens, and at the same time make the structure of the optical lens compact, which is conducive to the miniaturization of the optical lens.

[0067] In some embodiments, the liquid lens includes, in sequence from the object side to the imaging surface, a first surface, a second surface, a third surface, a fourth surface, a fifth surface, and a sixth surface. Among them, an aperture stop is provided at the second surface to converge the range of the light rays emitted by the front optical system; the first surface, the second surface, the fourth surface, the fifth surface, and the sixth surface are all flat surfaces, and the third surface is a curved surface and can have different radius of curvatures according to different applied driving voltages, and thus the liquid lens can have different optical powers. More specifically, when the optical lens starts to work, a certain starting voltage will be applied to the liquid lens according to the current working object distance. At this time, the third surface in the liquid lens will exhibit a certain radius of curvature, and the liquid lens will have a corresponding focal length, and it will be paired with the front and rear groups to 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 an appropriate focal length (the overall focal length of the optical lens is adjusted within a small range), realizing the function of automatic focusing, so that the optical lens has a high resolution at different working object distances.

[0068] In some embodiments, when the working object distance OBJ of the optical lens satisfies 500 mm ≤ OBJ ≤ 1500 mm, the driving voltage U applied to the liquid lens satisfies: 35 V < U < 48 V, and the focal length fb of the liquid lens can be positive or negative. That is, when the optical lens works at a certain range of working object distances, the driving voltage applied to the liquid lens will be automatically adjusted within a certain range. At this time, the liquid lens will have a positive optical power or a negative optical power due to the corresponding change in the radius of curvature of the third surface. More specifically, when the working object distance OBJ of the optical lens satisfies 500 mm ≤ OBJ ≤ 1500 mm, the driving voltage U applied to the liquid lens satisfies: 35 V < U < 48 V, and the radius of curvature of the third surface in the liquid lens will change accordingly, and the focal length of the liquid lens will also show different values. That is, at different working object distances (500 mm ≤ OBJ ≤ 1500 mm), by changing the driving voltage (35 V < U < 48 V) applied to the liquid lens, the radius of curvature of the liquid lens can be changed, and thus the liquid lens can exhibit different focal lengths to meet the requirement that the optical lens has a relatively clear imaging quality at different object distances, that is, to realize the fast automatic focusing function of the optical lens at different object distances.

[0069] In some embodiments, the object distance OBJ of the optical lens and the effective focal length f of the optical lens satisfy: 0.008 < OBJ / f < 0.04, and 14.5 mm < f < 18 mm. Meeting the above ranges can make the optical lens have a smaller working distance, which is beneficial to achieving high-definition shooting of relatively close objects by the optical lens and better realizing the higher resolution of the lens at different object distances.

[0070] In some embodiments, the effective focal length fa of the first group and the effective focal length f of the optical lens satisfy: 1.5 < fa / f < 2.5. Meeting the above ranges is beneficial to the smooth transition of light by reasonably setting the proportion of the focal length of the first group before the liquid lens, making the light 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 lens has high imaging quality at different working object distances.

[0071] In some embodiments, the effective focal length fc of the second group and the effective focal length f of the optical lens satisfy: 0.8 < fc / f < 1.5. Meeting the above ranges can effectively correct the aberration brought by the first group and the liquid lens by reasonably setting the proportion of the focal length of the second group after the liquid lens, so that the optical lens has better imaging quality at different working object distances.

[0072] In some embodiments, the effective focal length fa of the first group and the effective focal length fc of the second group satisfy: 1.5 < fa / fc < 3. Meeting the above ranges can be paired with the variable-focus liquid lens by reasonably setting the focal length ratio of the front and rear lens groups of the liquid lens, quickly realizing the automatic focusing of the system, and ensuring that the lens can achieve high-definition resolution at different working object distances.

[0073] In some embodiments, the effective focal length f1 of the first lens and the effective focal length f of the optical lens satisfy: 1 < f1 / f < 2. Meeting the above ranges can make the light entering the first lens converge well into the optical system by reasonably setting the focal length of the first lens, reducing the difficulty of aberration correction, ensuring the imaging quality of the optical lens, and at the same time enabling the optical system to have a larger light flux and improving the imaging illuminance of the optical lens.

[0074] In some embodiments, the effective focal length f2 of the second lens and the effective focal length f of the optical lens satisfy: 1 < f2 / f < 2; the curvature radius R3 of the object side of the second lens and the curvature radius R4 of the image side of the second lens satisfy: 0.3 < R3 / R4 < 0.6. Meeting the above ranges can further converge the incident light by reasonably setting the focal length and surface type of the second lens, promoting the miniaturization of the structure of the lens.

[0075] In some embodiments, the effective focal length f3 of the third lens and the effective focal length f of the optical lens satisfy: -1 < f3 / f < -0.5; the radius of curvature R5 of the object side of the third lens and the radius of curvature R6 of the image side of the third lens satisfy: -10 < R5 / R6 < -2. By setting the third lens to have a relatively large negative refractive power within the above ranges, the incident light can be appropriately diverged, allowing the light to enter the liquid lens at a relatively gentle angle, reducing the difficulty of correcting aberrations at different working object distances, and improving the imaging resolution at different working object distances.

[0076] In some embodiments, the effective focal length f4 of the fourth lens and the effective focal length f of the optical lens satisfy: 0.1 < f4 / f < 0.4. By setting the fourth lens to have a relatively large positive refractive power within the above ranges, the light exiting from the liquid lens can be effectively converged, reducing the influence of the liquid lens on the system sensitivity and relative illumination, and ensuring that the lens has high imaging quality at different working object distances.

[0077] In some embodiments, the effective focal length f5 of the fifth lens and the effective focal length f of the optical lens satisfy: -0.7 < f5 / f < -0.2; the radius of curvature R13 of the object side of the fourth lens and the radius of curvature R15 of the image side of the fifth lens satisfy: -6 < R13 / R15 < -1. By reasonably setting the optical power and surface shape of the fifth lens within the above ranges, on the one hand, it can cooperate with the fourth lens to reasonably correct the chromatic aberration of the system and improve the imaging quality of the optical system.

[0078] In some embodiments, the effective focal length f6 of the sixth lens and the effective focal length f of the optical lens satisfy: -0.8 < f6 / f < -0.2; the radius of curvature R16 of the object side of the sixth lens and the radius of curvature R17 of the image side of the sixth lens satisfy: -0.35 < R16 / R17 < -0.1. By reasonably setting the optical power and surface shape of the sixth lens within the above ranges, it is beneficial for the light to transition smoothly, balance various aberrations generated by the previous lenses, and at the same time, it can expand the height of the light exiting from the liquid lens to obtain a larger image height.

[0079] In some embodiments, the effective focal length f7 of the seventh lens and the effective focal length f of the optical lens satisfy: 0.5 < f7 / f < 1. By reasonably setting the optical power of the seventh lens within the above ranges, the convergence of light can be accelerated, thereby increasing the height of light focusing, while increasing the photosensitive area of the image plane and effectively improving the imaging quality of the optical system.

[0080] In some embodiments, the overall optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.3 < TTL / f < 1.7. By satisfying the above ranges, while meeting miniaturization requirements, it can ensure that light converges better on the imaging plane, which is beneficial for achieving a larger imaging plane.

[0081] In some embodiments, the image height IH corresponding to the maximum field angle of the optical lens and the effective focal length f of the optical lens satisfy: 0.6 < IH / f < 0.8. Meeting the above range can not only achieve the telephoto characteristics of the optical lens, enabling the optical lens to capture high-definition images even at a relatively short working object distance, but also achieve the large image plane characteristics of the optical lens, presenting more image details and realizing high-pixel imaging of the lens.

[0082] In some embodiments, the effective focal length f1 of the first lens and the effective focal length f7 of the seventh lens satisfy: 1.5 < f1 / f7 < 2; the effective aperture DM11 of the object side of the first lens and the effective aperture DM72 of the image side of the seventh lens satisfy: 0.8 < DM11 / DM72 < 1.2. Meeting the above range, by reasonably setting the focal length and aperture relationship of the head and tail lenses, while ensuring that as much light as possible enters the system, the area of light entering the image plane is increased, achieving high relative illuminance and large image plane imaging of the lens.

[0083] In some embodiments, the combined focal length f45 of the fourth lens and the fifth lens and the effective focal length f of the optical lens satisfy: 0.5 < f45 / f < 1; the effective focal length f4 of the fourth lens and the effective focal length f5 of the fifth lens satisfy: -0.8 < f4 / f5 < -0.2. Meeting the above range, by reasonably configuring the proportion of the focal lengths of the fourth lens and the fifth lens in the cemented lens, on the one hand, the chromatic aberration of the lens can be effectively eliminated, and on the other hand, the mirror reflection ghost image between the fourth lens and the fifth lens can be effectively eliminated, improving the imaging quality of the lens.

[0084] In some embodiments, the effective focal length f2 of the second lens and the effective focal length f3 of the third lens satisfy: -2.5 < f2 / f3 < -1.5. Meeting the above range, by reasonably controlling the focal length ratio of the second and third lenses, it is beneficial for the light to transition smoothly, reducing the correction difficulty of aberration and the sensitivity of the optical lens, and improving the imaging quality of the optical lens.

[0085] In some embodiments, the effective focal length f6 of the sixth lens and the effective focal length f7 of the seventh lens satisfy: -1 < f6 / f7 < -0.5. Meeting the above range can effectively slow down the degree of light convergence, increase the incident light entering the image plane, and better achieve large image plane imaging of the lens.

[0086] As an embodiment, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens can be made of all-glass lenses or a combination of glass and plastic, 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 a glass lens.

[0087] 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.

[0088] First Embodiment

[0089] 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 S24, the following components in sequence: 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, a seventh lens L7, a filter G1, and a protective glass G2. The optical centers of each lens are located on the same straight line.

[0090] Among them, the first lens L1 has positive optical power, and its object-side surface S1 and image-side surface S2 are convex; the second lens L2 has positive optical power, its object-side surface S3 is convex, and its image-side surface S4 is concave; the third lens L3 has negative optical power, its object-side surface S5 is concave, and its image-side surface S4 is concave; the fourth lens L4 has positive optical power, its object-side surface S13 is convex, and its image-side surface S4 is convex; the fifth lens L5 has negative optical power, and its object-side surface S13 is convex, and its image-side surface S4 is concave. The object-side surface S15 of the fifth lens is concave, and the object-side surface S16 and the image-side surface S17 of the sixth lens are concave. The object-side surface S18 and the image-side surface S19 of the seventh lens are convex. The object-side surface S20 and the image-side surface S21 of the filter G1 are both flat. The object-side surface S22 and the image-side surface S23 of the protective glass G2 are both flat.

[0091] Please see Figure 11, as shown is a schematic structural diagram of a liquid lens E1 provided by the present invention. The liquid lens E1 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 from the object side to the imaging plane. Among them, the aperture stop is provided at the second surface S8. The first surface S7, the second surface S8, the fourth surface S10, the fifth surface S11, and the sixth surface S12 are all flat surfaces, and the third surface S9 is a curved surface and can have different curvature radii according to different applied driving voltages, and thus the liquid lens E1 can have different optical powers. For example, when the working object distance OBJ of the optical lens satisfies: 500mm ≤ OBJ ≤ 1500mm, the driving voltage U applied to the liquid lens satisfies: 35V < U < 48V, and the liquid lens can present a positive focal length or a negative focal length.

[0092] In this embodiment, when the working object distance OBJ of the optical lens satisfies: 500mm ≤ OBJ ≤ 1500mm, the driving voltage U applied to the liquid lens satisfies: 38.5V < U < 41.6V. At this time, the curvature radius R9 of the third surface satisfies: R9 ∈ (-∞, -40.6) & (64.4, +∞), and the focal length fb of the liquid lens satisfies: fb ∈ (-∞, -725) & (1148, +∞). The overall effective focal length of the lens is adjusted within a small range of 15.8 - 16.1mm, and the imaging resolution basically does not change within different working object distances.

[0093] The relevant parameters of each lens of the optical lens 100 provided in this embodiment are shown in Table 1. [[ID=!]]

[0094] Table 1

[0095]

[0096]

[0097] Figure 2 Shows the vertical chromatic aberration curve graph of this embodiment, which represents the chromatic aberration of each wavelength relative to the central wavelength (0.570μm) at different image heights on the imaging plane. The horizontal axis represents the vertical chromatic aberration value of each wavelength relative to the central wavelength (unit: μm), and the vertical axis represents the normalized field angle. It can be seen from the figure that the vertical chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±1μm, indicating that the optical lens can excellently correct the chromatic aberration of the edge field and the secondary spectrum of the entire image plane.

[0098] Figure 3The relative illuminance curve of this embodiment is shown, which represents the relative illuminance values (unit: %) at different image heights on the imaging surface. The horizontal axis represents the image height (unit: mm), and the vertical axis represents the relative illuminance value. It can be seen from the figure that the relative illuminance value of the optical lens is still greater than 85% at the maximum semi-image height, indicating that the optical lens has good relative illuminance.

[0099] Figure 4 The modulation transfer function (MTF) curve of this embodiment is shown, which represents the modulation of the lens imaging 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. It can be seen from the figure that the MTF value of this embodiment is above 0.4 in the entire field of view. In the range of 0 - 148 lp / mm, the MTF curve decreases uniformly and smoothly from the center to the edge field of view, and has good imaging quality and good detail resolution ability in both low-frequency and high-frequency cases.

[0100] Second Embodiment

[0101] The optical lens provided in the second embodiment of the present invention has a substantially the same structure as the optical lens 100 in the first embodiment. The main differences are as follows: the curvature radius, thickness, spacing between each lens, and material of each lens are different. And when the object distance OBJ of the optical lens satisfies: 500 mm ≤ OBJ ≤ 1500 mm, the driving voltage U applied to the liquid lens satisfies: 40.2 V < U < 43.8 V. At this time, the curvature radius R9 of the third surface of the liquid lens satisfies: R9 ∈ (-∞, -314) & (22.3, +∞), and the focal length fb of the liquid lens satisfies: fb ∈ (-∞, -6749) & (394, +∞). The overall effective focal length of the lens is adjusted within a small range of 15.8 - 16.1 mm, and the imaging resolution basically does not change within different object distances.

[0102] The relevant parameters of each lens of the optical lens provided in this embodiment are shown in Table 2.

[0103] Table 2

[0104]

[0105]

[0106] Figures 5 to 7 The vertical chromatic aberration curve, relative illuminance curve, and MTF curve of this embodiment are shown respectively. From Figure 5 it can be seen that the vertical chromatic aberration between the longest wavelength and the shortest wavelength is controlled within ±0.5 μm, indicating that this optical lens can excellently correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image plane. From Figure 6It can be seen that the relative illumination value of the optical lens at the maximum semi-image height is still greater than 85%, indicating that the optical lens has good relative illumination. From Figure 7 It can be seen that the MTF value is above 0.35 within the entire field of view. In the range of 0 to 148 lp / mm, the MTF curve smoothly decreases uniformly from the center to the edge of the field of view, and it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency cases.

[0107] The Third Embodiment

[0108] The optical lens provided by the third embodiment of the present invention has a structure substantially the same as that of the optical lens 100 in the first embodiment. The main differences are as follows: the curvature radius, thickness, spacing between each lens, and material of each lens are different. And when the object distance OBJ of the optical lens satisfies: 500 mm ≤ OBJ ≤ 1500 mm, the driving voltage U applied to the liquid lens satisfies: 40.9 V < U < 44.4 V. At this time, the curvature radius R9 of the third surface satisfies: R9 ∈ (18.6, 165), the focal length fb of the liquid lens satisfies fb ∈ (-337, 3358), and the overall effective focal length of the lens is adjusted within a small range of 15.8 to 16.1 mm, and the imaging resolution basically does not change within different object distances.

[0109] The relevant parameters of each lens of the optical lens 300 provided in this embodiment are shown in Table 3.

[0110] Table 3

[0111]

[0112]

[0113] Figures 8 to 10 Respectively show the vertical chromatic aberration curve graph, relative illumination curve graph and MTF curve graph of this embodiment. From Figure 8 It can be seen that the vertical chromatic aberration between the longest wavelength and the shortest wavelength is controlled within ±1 μm, indicating that the optical lens can excellently correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image plane. From Figure 9 It can be seen that the relative illumination value of the optical lens at the maximum semi-image height is still greater than 85%, indicating that the optical lens has good relative illumination. From Figure 10 It can be seen that the MTF value is above 0.35 within the entire field of view. In the range of 0 to 148 lp / mm, the MTF curve smoothly decreases uniformly from the center to the edge of the field of view, and it has good imaging quality and good detail resolution ability in both low-frequency and high-frequency cases.

[0114] Please refer to Table 4, which shows the optical characteristics of the optical lenses provided in the three embodiments above, including the total optical length TTL, effective focal length f, maximum field of view FOV, image height IH corresponding to the maximum field of view, working object distance OBJ, driving voltage U of the liquid lens, and effective focal length fb of the liquid lens. It also includes the relevant values ​​corresponding to each condition in the above conditional expressions.

[0115] Table 4

[0116]

[0117]

[0118] In summary, the optical lens provided by this invention has at least the following advantages:

[0119] (1) The optical lens provided by the present invention adopts a combination of seven glass lenses and one liquid lens. By reasonably allocating the liquid lens and the focal length relationship of each lens, the optical lens has better imaging capability at different object distances. At the same time, by reasonably configuring the thickness, spacing and surface shape of each lens, the optical lens has advantages such as long focal length, small total length, high relative illumination, large image plane, high resolution and autofocus.

[0120] (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 500mm to 1500mm) 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.

[0121] (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.

[0122] (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.

[0123] 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.

[0124] 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 two groups and a liquid lens, characterized in that, It sequentially includes from the object side to the imaging surface along the optical axis: The first group with positive optical power, which consists of three lenses. The first group sequentially includes from the object side to the imaging surface a first lens with positive optical power, a second lens with positive optical power, and a third lens with negative optical power; A liquid lens with optical power, and the liquid lens presents different focal lengths according to different applied voltages; The second group with positive optical power, which consists of four lenses. The second group sequentially includes from the object side to the imaging surface a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with negative optical power, and a seventh lens with positive optical power; Wherein, the effective focal length fa of the first group and the effective focal length fc of the second group satisfy: 1.5 < fa / fc < 3.0; The image height IH corresponding to the maximum field angle of the optical lens and the effective focal length f of the optical lens satisfy: 0.6 < IH / f < 0.

8.

2. The optical lens according to claim 1, characterized in that, The working object distance OBJ of the optical lens and the effective focal length f of the optical lens satisfy: 0.008 < OBJ / f < 0.04, 14.5 mm < f < 18 mm.

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

4. The optical lens according to claim 1, characterized in that, The effective focal length f2 of the second lens and the effective focal length f of the optical lens satisfy: 1 < f2 / f < 2.

5. The optical lens according to claim 1, characterized in that, The effective focal length f3 of the third lens and the effective focal length f of the optical lens satisfy: -1 < f3 / f < -0.

5.

6. The optical lens according to claim 1, characterized in that, The effective focal length f4 of the fourth lens and the effective focal length f of the optical lens satisfy: 0.1 < f4 / f < 0.

4.

7. The optical lens according to claim 1, characterized in that, The effective focal length f5 of the fifth lens and the effective focal length f of the optical lens satisfy: -0.7 < f5 / f < -0.

2.

8. The optical lens according to claim 1, characterized in that, The effective focal length f6 of the sixth lens and the effective focal length f of the optical lens satisfy: -0.8 < f6 / f < -0.2; the effective focal length f7 of the seventh lens and the effective focal length f of the optical lens satisfy: 0.5 < f7 / f < 1.

9. The optical lens according to claim 1, characterized in that, The effective focal length f1 of the first lens and the effective focal length f7 of the seventh lens satisfy: 1.5 < f1 / f7 < 2; the effective aperture DM11 of the object side of the first lens and the effective aperture DM72 of the image side of the seventh lens satisfy: 0.8 < DM11 / DM72 < 1.

2.

10. The optical lens according to claim 1, characterized in that, The combined focal length f45 of the fourth lens and the fifth lens and the effective focal length f of the optical lens satisfy: 0.5 < f45 / f < 1; the effective focal length f4 of the fourth lens and the effective focal length f5 of the fifth lens satisfy: -0.8 < f4 / f5 < -0.

2.

11. The optical lens according to claim 1, characterized in that, The effective focal length fa of the first group and the effective focal length fc of the second group satisfy: 1.757 ≤ fa / fc ≤ 2.206; The image height IH corresponding to the maximum field angle of the optical lens and the effective focal length f of the optical lens satisfy: 0.689 ≤ IH / f ≤ 0.

703.

12. The optical lens according to claim 1, characterized in that, The object-side surface of the first lens is convex, and the image-side surface of the first lens is convex; the object-side surface of the second lens is convex, and the image-side surface of the second lens is concave; the object-side surface of the third lens is concave, and the image-side surface of the third lens is concave; the object-side surface of the fourth lens is convex, and the image-side surface of the fourth lens is convex; the object-side surface of the fifth lens is concave, and the image-side surface of the fifth lens is convex; the object-side surface of the sixth lens is concave, and the image-side surface of the sixth lens is concave; the object-side surface of the seventh lens is convex, and the image-side surface of the seventh lens is convex.

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