Optical lens

Abstract

The application provides an optical lens, which comprises, in sequence from an object side to an imaging surface along an optical axis, a first lens with positive focal power, the object side of which is a convex surface; a second lens with positive focal power, the object side of which is a convex surface; a third lens with negative focal power, the image side of which is a concave surface; a fourth lens with negative focal power, the object side of which is a concave surface; a fifth lens with positive focal power, the image side of which is a convex surface; a sixth lens with negative focal power; and a seventh lens with positive focal power, the image side of which is a convex surface. The optical lens has the advantages of high pixels, small distortion and good thermal stability by reasonably matching the lens shapes and focal power combinations between the lenses.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of imaging lenses, in particular to an optical lens. BACKGROUND

[0002] In recent years, with the development of the automation industry, machine vision has achieved explosive growth, and the application field of industrial lenses is also more and more extensive. Due to the characteristics of high resolution, high definition and good stability, industrial lenses are widely used in size measurement, defect detection, image acquisition and other fields.

[0003] In order to achieve good imaging effect, such industrial lenses usually require high resolution, small picture distortion, and high relative luminance to ensure the uniformity of picture luminance. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide an optical lens which can solve one or more of the above problems.

[0005] To achieve the above purpose, the present application provides an optical lens, which is sequentially arranged along the optical axis from the object side to the imaging surface: a first lens with positive focal power, the object side surface of which is convex; a second lens with positive focal power, the object side surface of which is convex; a third lens with negative focal power, the image side surface of which is concave; a fourth lens with negative focal power, the object side surface of which is concave; a fifth lens with positive focal power, the image side surface of which is convex; a sixth lens with negative focal power; a seventh lens with positive focal power, the image side surface of which is convex.

[0006] Compared with the prior art, the optical lens provided by the present application has the advantages of reasonable focal power distribution, surface type matching, lens thickness and lens spacing, and has the advantages of high pixel, small distortion and miniaturization. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 It is a structure schematic diagram of the optical lens of embodiment 1 of the present application.

[0008] Figure 2 It is an optical distortion curve diagram of the optical lens in embodiment 1 of the present application.

[0009] Figure 3 It is a curve diagram of the sagittal chromatic aberration of the optical lens in embodiment 1 of the present application.

[0010] Figure 4 It is a curve diagram of the lateral chromatic aberration of the optical lens in embodiment 1 of the present application.

[0011] Figure 5 It is an MTF curve diagram of the optical lens in embodiment 1 of the present application.

[0012] Figure 6 Structure diagram of the optical lens of embodiment 2 of the present application.

[0013] Figure 7 Optical distortion curve of the optical lens of embodiment 2 of the present application.

[0014] Figure 8 Curvature of the optical lens of embodiment 2 of the present application.

[0015] Figure 9 Curvature of the optical lens of embodiment 2 of the present application.

[0016] Figure 10 MTF curve of the optical lens of embodiment 2 of the present application.

[0017] Figure 11 Structure diagram of the optical lens of embodiment 3 of the present application.

[0018] Figure 12 Optical distortion curve of the optical lens of embodiment 3 of the present application.

[0019] Figure 13 Curvature of the optical lens of embodiment 3 of the present application.

[0020] Figure 14 Curvature of the optical lens of embodiment 3 of the present application.

[0021] Figure 15 MTF curve of the optical lens of embodiment 3 of the present application. DETAILED DESCRIPTION

[0022] For a better understanding of the present application, various aspects of the present application will be described in more detail below with reference to the accompanying drawings. It is to be understood that the detailed description is merely descriptive of embodiments of the present application and is not intended to limit the scope of the present application in any way. Throughout the specification, like reference numerals refer to like elements. The expression “and / or” includes any and all combinations of one or more of the associated listed items.

[0023] It should be noted that the expressions first, second, third, etc. in the present specification are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, the first lens discussed below can also be referred to as the second lens or the third lens without departing from the teachings of the present application.

[0024] In the drawings, the thickness, size, and shape of the lenses have been exaggerated slightly for ease of explanation. Specifically, the shape of the spherical or aspherical surface shown in the drawings is shown by way of example. That is, the shape of the spherical or aspherical surface is not limited to the shape of the spherical or aspherical surface shown in the drawings. The drawings are merely examples and are not drawn to scale.

[0025] In this document, the paraxial region refers to a region near the optical axis. If a lens surface is convex and the position of the convex surface is not specified, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the position of the concave surface is not specified, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is referred to as the object side surface of the lens, and the surface of each lens closest to the imaging surface is referred to as the image side surface of the lens.

[0026] It should also be understood that the use of the terms "including", "including have", "have", "contain" and / or "contain have", when used in this specification, indicates the presence of the stated features, elements and / or components, but does not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of" appear after a list of listed features, they modify the entire list of features and not the individual elements of the list. In addition, when describing embodiments of the present application, the use of "may" indicates "one or more embodiments of the present application". And the term "exemplary" is intended to refer to an example or illustration.

[0027] Unless otherwise defined, all terms used in this document, including technical terms and scientific terms, have the same meaning as commonly understood by those skilled in the art to which the present application belongs. It should also be understood that terms (such as terms defined in common dictionaries) should be interpreted in accordance with their meanings in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense, unless otherwise defined herein.

[0028] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with embodiments.

[0029] The optical lens according to an embodiment of the present application comprises a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens and a filter.

[0030] Specifically, the first lens has positive refractive power, the object side surface is convex, and the image side surface is concave; the second lens has positive refractive power, the object side surface is convex, and the image side surface is convex; the third lens has negative refractive power, the object side surface is concave, and the image side surface is concave; the fourth lens has negative refractive power, the object side surface is concave, and the image side surface is concave; the fifth lens has positive refractive power, the object side surface is convex, and the image side surface is convex; the sixth lens has negative refractive power, the object side surface is concave, and the image side surface is convex; and the seventh lens has positive refractive power, the object side surface is convex, and the image side surface is convex. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all glass spherical lenses.

[0031] In some embodiments, a diaphragm can be arranged between the third lens and the fourth lens to confine the range of light exiting the front end of the optical lens to enter the rear end lens group.

[0032] In some embodiments, the second lens and the third lens can be cemented to form a cemented lens, or the fourth lens and the fifth lens can be cemented to 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.

[0033] In some embodiments, the total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.2 < TTL / f < 1.7. Satisfying the above range is conducive to controlling the overall length and volume of the optical lens, and realizing the miniaturization of the optical lens.

[0034] In some embodiments, the image height IH corresponding to the maximum half field angle of the optical lens and the effective focal length f of the optical lens satisfy: 0.18 < IH / f < 0.30. Satisfying the above range is conducive to controlling the field angle range of the optical lens, so that the optical lens satisfies the required field angle.

[0035] In some embodiments, the total optical length TTL of the optical lens, the image height IH corresponding to the maximum half field angle of the optical lens, and the maximum half field angle θ of the optical lens satisfy: 0.40 / ° < TTL / IH / θ < 0.52 / °. Satisfying the above range is conducive to controlling the imaging range of the optical lens, and meeting the requirements of the chip.

[0036] In some embodiments, the combined focal length f123 of the first lens, the second lens, and the third lens and the effective focal length f of the optical lens satisfy: 0.7 < f123 / f < 1.2. Satisfying the above range is conducive to eliminating high-order aberrations of the optical lens, improving the resolution, and optimizing the imaging effect of the optical lens.

[0037] In some embodiments, the effective focal length f2 of the second lens and the effective focal length f3 of the third lens satisfy: -1.5 < f2 / f3 < -1.0; the center thickness CT2 of the second lens and the center thickness CT3 of the third lens satisfy: 3.3 < CT2 / CT3 < 3.6. Satisfying the above ranges is conducive to controlling the optical power of the cemented lens while ensuring the feasibility of its processing.

[0038] In some embodiments, the air separation AT34 on the optical axis between the third lens and the fourth lens and the total optical length TTL of the optical lens satisfy: 0.04 < AT34 / TTL < 0.07. Satisfying the above ranges is conducive to controlling the spacing of the two cemented lenses before and after the stop, facilitating the correction of the chromatic aberration of the optical lens.

[0039] In some embodiments, the combined focal length f45 of the fourth lens and the fifth lens and the effective focal length f6 of the sixth lens satisfy: -10.0 < f45 / f6 < -4.0; the center thickness CT4 of the fourth lens, the center thickness CT5 of the fifth lens, the air separation AT56 on the optical axis between the fifth lens and the sixth lens, and the center thickness CT6 of the sixth lens satisfy: 0.95 < (CT4+CT5+AT56) / CT6 < 1.35. Satisfying the above ranges is conducive to correcting the spherical aberration of the optical lens while effectively controlling the length and volume of the optical lens, achieving a balance between high pixels and miniaturization of the optical lens.

[0040] 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 < 1.0; the center thickness CT7 of the seventh lens and the total optical length TTL of the optical lens satisfy: 0.08 < CT7 / TTL < 0.15. Satisfying the above ranges can control the angle of the outgoing light of the optical lens, making it better adapt to the light receiving range of the chip.

[0041] In some embodiments, the radius of curvature R1 of the object side surface of the first lens and the effective focal length f of the optical lens satisfy: 0.5 < R1 / f < 1.0. Satisfying the above ranges is conducive to controlling the surface shape of the first lens, making the optical lens meet the light receiving demand.

[0042] In some embodiments, the distance STL on the optical axis between the stop and the imaging surface and the total optical length TTL of the optical lens satisfy: 0.70 < STL / TTL < 0.83. Satisfying the above ranges can reasonably set the position of the stop, improve the light throughput of the optical lens, enhance the resolution, and correct part of the aberration.

[0043] The application will be further described in the following embodiments. In each embodiment, the thickness, the radius of curvature and the material selection of each lens in the optical lens are different, and the specific differences can be seen from the parameter table of each embodiment. The following embodiments are only the preferred embodiments of the application, but the embodiments of the application are not limited to the following embodiments only, and any changes, substitutions, combinations or simplifications made without departing from the innovative points of the application should be regarded as equivalent replacement methods and are included in the protection scope of the application.

[0044] Embodiment 1

[0045] Please refer to Figure 1 , which is a structural schematic diagram of the optical lens provided in embodiment 1 of the application. The optical lens includes, along the optical axis from the object side to the imaging surface S15, a first lens L1, a second lens L2, a third lens L3, a diaphragm ST, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7 and a filter G1.

[0046] Specifically, the first lens L1 has positive focal power, the object side S1 is a convex surface, and the image side S2 is a concave surface; the second lens L2 has positive focal power, the object side S3 is a convex surface, and the image side is a convex surface; the third lens L3 has negative focal power, the object side is a concave surface, and the image side S5 is a concave surface; the fourth lens L4 has negative focal power, the object side S6 is a concave surface, and the image side is a concave surface; the fifth lens L5 has positive focal power, the object side is a convex surface, and the image side S8 is a convex surface; the sixth lens L6 has negative focal power, the object side S9 is a concave surface, and the image side S10 is a convex surface; the seventh lens L7 has positive focal power, the object side S11 is a convex surface, and the image side S12 is a convex surface; the filter G1 has a flat object side S13 and a flat image side S14; wherein the second lens L2 and the third lens L3 are glued to form a glued lens, and the gluing surface is S4; the fourth lens L4 and the fifth lens L5 are glued to form a glued lens, and the gluing surface is S7.

[0047] The related parameters of each lens in the optical lens in embodiment 1 are shown in Table 1.

[0048] Table 1

[0049]

[0050] Figure 2 The optical distortion curve of embodiment 1 is shown, which represents the distortion at different fields of view on the imaging surface. The horizontal axis represents the percentage, and the vertical axis represents the half field of view (unit: °). As can be seen from the figure, the optical distortion of the present embodiment is controlled within ±6%, which indicates that the distortion of the optical lens is well corrected.

[0051] Figure 3The diagram shows the transverse chromatic aberration curves for Example 1, representing the chromatic aberration of each wavelength relative to the center wavelength (0.555 μm) at different image heights on the imaging plane. The horizontal axis represents the transverse chromatic aberration value (unit: μm) of each wavelength relative to the center wavelength, and the vertical axis represents the normalized field of view. As can be seen from the diagram, the transverse chromatic aberration of the longest and shortest wavelengths is controlled within ±1.0 μm, indicating that the optical lens can excellently correct chromatic aberration at the edge of the field of view and the secondary spectrum of the entire image plane.

[0052] Figure 4 The axial chromatic aberration curve of Example 1 is shown, which represents the aberration of each wavelength on the optical axis at the imaging plane. The horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the axial chromatic aberration offset is controlled within ±0.08 mm, indicating that the optical lens can effectively correct axial chromatic aberration.

[0053] Figure 5 The modulation transfer function (MTF) curve of Example 1 is shown, which represents the 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 example is above 0.5 throughout the entire field of view. In the range of 0 to 150 lp / mm, the MTF curve decreases smoothly and uniformly from the center to the edge of the field of view, exhibiting good imaging quality and good detail resolution at both low and high frequencies.

[0054] Example 2

[0055] Please see Figure 6 The figure shows a schematic diagram of the structure of the optical lens provided in Embodiment 2 of the present invention. The optical lens in this embodiment has a similar structure to the optical lens in Embodiment 1. The main differences are that the curvature radius, center thickness, edge thickness and material of each lens are different.

[0056] The relevant parameters of each lens in the optical lens of Example 2 are shown in Table 2.

[0057] Table 2

[0058]

[0059]

[0060] Figures 7 to 10The optical distortion curve, the vertical color aberration curve, the axial color aberration curve and the modulation transfer function (MTF) curve of the optical lens provided in the embodiment 2 are shown in the figures. As can be seen from the figures, the optical distortion of the embodiment is controlled within ±8%, which indicates that the distortion of the optical lens is well corrected; the vertical color aberration of the longest wavelength and the shortest wavelength is controlled within ±1.0 μm, which indicates that the optical lens can well correct the color aberration of the edge field and the secondary spectrum of the whole image plane; the offset of the axial color aberration is controlled within ±0.08 mm, which indicates that the optical lens can well correct the axial color aberration; the MTF value of the embodiment is above 0.5 in the whole field of view, and in the range of 0-150 lp / mm, the MTF curve is uniformly and smoothly decreased from the center to the edge field, and the imaging quality and the detail resolution ability are good in the low frequency and high frequency conditions.

[0061] Embodiment 3

[0062] Please refer to Figure 11 , which is a structural schematic view of the optical lens provided in the embodiment 3 of the present application. The optical lens in the embodiment is substantially the same as the optical lens in the embodiment 1 in structure and shape, and the difference mainly lies in that the curvature radius, the center thickness and the edge thickness of each lens are changed.

[0063] The related parameters of each lens in the optical lens in the embodiment 3 are shown in Table 3.

[0064] Table 3

[0065]

[0066]

[0067] Figures 12 to 15 The optical distortion curve, the vertical color aberration curve, the axial color aberration curve and the modulation transfer function (MTF) curve of the optical lens provided in the embodiment 3 are shown in the figures. As can be seen from the figures, the optical distortion of the embodiment is controlled within ±7%, which indicates that the distortion of the optical lens is well corrected; the vertical color aberration of the longest wavelength and the shortest wavelength is controlled within ±1.0 μm, which indicates that the optical lens can well correct the color aberration of the edge field and the secondary spectrum of the whole image plane; the offset of the axial color aberration is controlled within ±0.07 mm, which indicates that the optical lens can well correct the axial color aberration; the MTF value of the embodiment is above 0.46 in the whole field of view, and in the range of 0-150 lp / mm, the MTF curve is uniformly and smoothly decreased from the center to the edge field, and the imaging quality and the detail resolution ability are good in the low frequency and high frequency conditions.

[0068] Please refer to Table 4 for the optical characteristics of the above-mentioned embodiments, including the effective focal length f, the maximum half field angle θ, the entrance pupil diameter EPD, the total track length TTL, the F-number FNO, the image height IH, and the numerical values corresponding to each conditional expression in the embodiments.

[0069] Table 4

[0070]

[0071]

[0072] In summary, the optical lens provided by the present application can have a field of view angle greater than 25°, a total track length less than 51mm, optical distortion controlled within ±8%, transverse chromatic aberration controlled within ±1.0μm, axial chromatic aberration offset controlled within ±0.08mm, and MTF values in the full field of view all greater than 0.46, i.e., the optical lens can achieve a balance of high pixels, small distortion, and miniaturization.

[0073] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0074] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. An optical lens, in total seven pieces of lenses, characterized in that, In order from the object side to the imaging plane along the optical axis are: a first lens with positive refractive power, an object side surface of the first lens being convex; a second lens with positive refractive power, an object side surface of the second lens being convex; a third lens with negative refractive power, an image side surface of the third lens being concave; a fourth lens with negative refractive power, an object side surface of the fourth lens being concave; a fifth lens with positive refractive power, an image side surface of the fifth lens being convex; a sixth lens with negative refractive power; a seventh lens with positive refractive power, an image side surface of the seventh lens being convex; an optical total track length TTL of the optical lens and an image height IH corresponding to a maximum half field angle of the optical lens and the maximum half field angle θ of the optical lens satisfy: 0.40 / ° < TTL / IH / θ < 0.52 / °; a combined focal length f123 of the first lens, the second lens and the third lens and an effective focal length f of the optical lens satisfy: 0.7 < f123 / f < 1.

2.

2. The optical lens of claim 1, wherein, The second lens and the third lens are cemented to form a cemented lens.

3. The optical lens of claim 1, wherein, The fourth lens and the fifth lens are cemented to form a cemented lens.

4. The optical lens of claim 1, wherein, An optical total track length TTL of the optical lens and an effective focal length f of the optical lens satisfy: 1.2 < TTL / f < 1.

7.

5. The optical lens of claim 1, wherein, An image height IH corresponding to a maximum half field angle of the optical lens and an effective focal length f of the optical lens satisfy: 0.18 < IH / f < 0.

30.

6. The optical lens of claim 1, wherein, An optical total track length TTL of the optical lens and an image height IH corresponding to a maximum half field angle of the optical lens and the maximum half field angle θ of the optical lens satisfy: 0.464 / ° ≤ TTL / IH / θ ≤ 0.478 / °.

7. The optical lens of claim 1, wherein, A combined focal length f123 of the first lens, the second lens and the third lens and an effective focal length f of the optical lens satisfy: 0.845 ≤ f123 / f ≤ 1.

018.

8. The optical lens of claim 1, wherein, An air interval AT34 on the optical axis between the third lens and the fourth lens and an optical total track length TTL of the optical lens satisfy: 0.04 < AT34 / TTL < 0.

07.

9. The optical lens of claim 1, wherein, A combined focal length f45 of the fourth lens and the fifth lens and an effective focal length f6 of the sixth lens satisfy: -10.0 < f45 / f6 < -4.

0.

10. The optical lens of claim 1, wherein, An effective focal length f7 of the seventh lens and an effective focal length f of the optical lens satisfy: 0.5 < f7 / f < 1.0.

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