CN116953892A - Optical lens - Google Patents

Abstract

The invention provides an optical lens, which sequentially comprises the following components from an object side to an imaging surface along an optical axis: a first lens with positive focal power, the object side surface of which is a convex surface; a second lens having positive optical power, the object side surface of which is a convex surface; a third lens having negative optical power, the image-side surface of which is concave; a fourth lens with negative focal power, the object side surface of which is a concave surface; a fifth lens having positive optical power, an image side surface of which is convex; a sixth lens having negative optical power; the seventh lens with positive focal power has a convex image side. The invention combines the lens shape and focal power among the lenses reasonably, so that the optical lens has the advantages of high pixels, small distortion and good thermal stability.

Description

Optical lens

Technical Field

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

Background

In recent years, with the development of the automation industry, the machine vision has exploded, and the application field of the industrial lens is more and more wide, and the industrial lens has the characteristics of high resolution, high definition, good stability and the like, so that the industrial lens is widely applied to the fields of size measurement, defect detection, image acquisition and the like.

In order to achieve good imaging effect, such industrial lenses are generally required to have high resolution, small picture distortion degree, and high relative illuminance, so as to ensure uniformity of picture illuminance.

Disclosure of Invention

In view of the foregoing, it is an object of the present invention to provide an optical lens capable of solving one or more of the above-mentioned problems.

In order to achieve the above object, the present invention provides an optical lens, in order from an object side to an imaging surface along an optical axis: a first lens with positive focal power, the object side surface of which is a convex surface; a second lens having positive optical power, the object side surface of which is a convex surface; a third lens having negative optical power, the image-side surface of which is concave; a fourth lens with negative focal power, the object side surface of which is a concave surface; a fifth lens having positive optical power, an image side surface of which is convex; a sixth lens having negative optical power; the seventh lens with positive focal power has a convex image side.

Compared with the prior art, the invention has the beneficial effects that: the optical lens provided by the invention has reasonable focal power distribution, surface collocation, lens thickness and inter-lens spacing, so that the optical lens has the advantages of high pixels, small distortion and miniaturization.

Drawings

Fig. 1 is a schematic structural diagram of an optical lens according to embodiment 1 of the present invention.

Fig. 2 is a graph showing optical distortion of the optical lens in embodiment 1 of the present invention.

Fig. 3 is a graph showing a vertical axis chromatic aberration of an optical lens in embodiment 1 of the present invention.

Fig. 4 is a graph showing lateral chromatic aberration of an optical lens in embodiment 1 of the present invention.

Fig. 5 is an MTF graph of the optical lens in example 1 of the present invention.

Fig. 6 is a schematic structural diagram of an optical lens according to embodiment 2 of the present invention.

Fig. 7 is a graph showing optical distortion of the optical lens in embodiment 2 of the present invention.

Fig. 8 is a graph showing a vertical axis chromatic aberration of an optical lens in embodiment 2 of the present invention.

Fig. 9 is a graph showing lateral chromatic aberration of an optical lens in embodiment 2 of the present invention.

Fig. 10 is an MTF graph of the optical lens in example 2 of the present invention.

Fig. 11 is a schematic structural diagram of an optical lens in embodiment 3 of the present invention.

Fig. 12 is a graph showing optical distortion of the optical lens in embodiment 3 of the present invention.

Fig. 13 is a graph showing a vertical axis chromatic aberration of an optical lens in embodiment 3 of the present invention.

Fig. 14 is a graph showing lateral chromatic aberration of an optical lens in embodiment 3 of the present invention.

Fig. 15 is an MTF graph of the optical lens in example 3 of the present invention.

Detailed Description

For a better understanding of 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 description are merely illustrative of embodiments of the invention and are not intended to limit the scope of the invention in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

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

In the drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for convenience of explanation. In particular, the spherical or aspherical shape 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 figures are merely examples and are not drawn to scale.

Herein, the paraxial region refers to a region near the optical axis. If the lens surface is convex and the convex position is not defined, then the lens surface is convex at least in the paraxial region; if the lens surface is concave and the concave position 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 object is referred to as the object side of the lens, and the surface of each lens closest to the imaging plane is referred to as the image side of the lens.

It will be further understood that the terms "comprises," "comprising," "includes," "including," "having," "containing," and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Furthermore, when a statement such as "at least one of the following" appears after a list of features that are listed, the entire listed feature is modified instead of modifying a separate element in the list. Furthermore, when describing embodiments of the invention, use of "may" means "one or more embodiments of the invention. Also, the term "exemplary" is intended to refer to an example or illustration.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.

The embodiment of the invention provides an optical lens, which sequentially comprises from an object side to an imaging surface along an optical axis: the optical lens 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 an optical filter.

Specifically, the first lens has positive focal power, and the object side surface of the first lens is a convex surface and the image side surface of the first lens is a concave surface; the second lens has positive focal power, and the object side surface of the second lens is a convex surface and the image side surface of the second lens is a convex surface; the third lens has negative focal power, and the object side surface of the third lens is a concave surface and the image side surface of the third lens is a concave surface; the fourth lens is provided with negative focal power, the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a concave surface; the fifth lens has positive focal power, and the object side surface of the fifth lens is a convex surface and the image side surface of the fifth lens is a convex surface; the sixth lens is provided with negative focal power, the object side surface of the sixth lens is a concave surface, and the image side surface of the sixth lens is a convex surface; the seventh lens has positive focal power, and the object side surface of the seventh lens is a convex surface and the image side surface of the seventh lens is a convex surface. 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.

In some embodiments, a diaphragm may be disposed between the third lens and the fourth lens to converge a range of light exiting from a front end of the optical lens to enter the rear end lens group.

In some embodiments, the second lens and the third lens may be cemented to form a cemented lens, or the fourth lens and the fifth lens may be cemented to form a cemented lens, so as to share chromatic aberration correction of the optical lens, improve resolution of the optical lens, and make the optical lens compact in structure, thereby being beneficial to achieving miniaturization of the optical lens.

In some embodiments, the optical total length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.2 < TTL/f < 1.7. The optical lens meets the range, is beneficial to controlling the whole length and the volume of the optical lens, and realizes the miniaturization of the optical lens.

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: IH/f is more than 0.18 and less than 0.30. The above range is satisfied, which is beneficial to control the field range of the optical lens, so that the optical lens satisfies the required field angle.

In some embodiments, the total optical length TTL of the optical lens and 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: TTL/IH is more than 0.40 and less than 0.52. The imaging range of the optical lens can be controlled, and the chip requirement can be met.

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. The range is satisfied, so that the high-order aberration of the optical lens is eliminated, the resolving power is improved, and the imaging effect of the optical lens is optimized.

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: CT2/CT3 is less than 3.3 and less than 3.6. The range is satisfied, the focal power of the cemented lens is favorably controlled, and the feasibility of processing is ensured.

In some embodiments, the air space AT34 between the third lens and the fourth lens on the optical axis and the total optical length TTL of the optical lens satisfy: 0.04 < AT34/TTL < 0.07. The range is satisfied, the interval between the two cemented lenses before and after the diaphragm is favorably controlled, and the chromatic aberration of the optical lens is convenient to correct.

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 interval AT56 on the optical axis between the fifth lens and the sixth lens, the center thickness CT6 of the sixth lens satisfy: 0.95 < (CT4+CT5+AT 56)/CT 6 < 1.35. The spherical aberration correction method meets the range, is favorable for correcting the spherical aberration of the optical lens, can effectively control the length and the volume of the optical lens, and realizes the balance of high pixels and miniaturization of the optical lens.

In some embodiments, the effective focal length f7 of the seventh lens and the effective focal length f of the optical lens satisfy: f7/f is more than 0.5 and less than 1.0; the center thickness CT7 of the seventh lens and the total optical length TTL of the optical lens satisfy: CT7/TTL 0.08 < 0.15. The range is satisfied, and the angle of the emergent light of the optical lens can be controlled, so that the optical lens is better adapted to the light receiving range of the chip.

In some embodiments, the radius of curvature R1 of the first lens object-side surface and the effective focal length f of the optical lens satisfy: r1/f is more than 0.5 and less than 1.0. The range is satisfied, the control of the surface shape of the first lens is facilitated, and the optical lens meets the light receiving requirement.

In some embodiments, the distance STL between the diaphragm and the imaging plane on the optical axis and the total optical length TTL of the optical lens satisfy: 0.70 < STL/TTL < 0.83. The range is satisfied, the position of the diaphragm can be reasonably set, the light flux of the optical lens is improved, the resolution is enhanced, and partial aberration is corrected.

The invention is further illustrated in the following examples. In various embodiments, the thickness, radius of curvature, and material selection portion of each lens in the optical lens may vary, and for specific differences, reference may be made to the parameter tables of the various embodiments. The following examples are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples, and any other changes, substitutions, combinations or simplifications that do not depart from the gist of the present invention are intended to be equivalent substitutes within the scope of the present invention.

Example 1

Referring to fig. 1, a schematic structural diagram of an optical lens provided in embodiment 1 of the present invention is shown, where the optical lens sequentially includes, along an optical axis from an object side to an imaging surface S15: the first lens L1, the second lens L2, the third lens L3, the stop ST, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the filter G1.

Specifically, the first lens element L1 has positive refractive power, wherein an object-side surface S1 thereof is convex, and an image-side surface S2 thereof is concave; the second lens element L2 has positive refractive power, wherein an object-side surface S3 thereof is convex and an image-side surface thereof is convex; the third lens L3 has negative focal power, wherein an object side surface is a concave surface, and an image side surface S5 is a concave surface; the fourth lens element L4 has negative refractive power, wherein an object-side surface S6 thereof is a concave surface, and an image-side surface thereof is a concave surface; the fifth lens element L5 with positive refractive power has a convex object-side surface and a convex image-side surface S8; the sixth lens element L6 with negative refractive power has a concave object-side surface S9 and a convex image-side surface S10; the seventh lens L7 has positive focal power, wherein an object side surface S11 is a convex surface, and an image side surface S12 is a convex surface; the optical filter G1, the object side surface S13 and the image side surface S14 of which are plane surfaces; the second lens L2 and the third lens L3 are glued to form a glued lens, and the glued surface is S4; the fourth lens L4 and the fifth lens L5 are bonded to form a bonding lens, and the bonding surface is S7.

The relevant parameters of each lens in the optical lens in example 1 are shown in table 1.

TABLE 1

Fig. 2 shows the optical distortion curve of example 1, which represents distortion at different fields of view on the imaging plane, the horizontal axis represents percent, and the vertical axis represents half field angle (in degrees). As can be seen from the figure, the optical distortion of the present embodiment is controlled within ±6%, which means that the distortion of the optical lens is well corrected.

Fig. 3 shows a vertical axis color difference graph of example 1, which represents color differences at different image heights on an imaging plane for each wavelength with respect to a center wavelength (0.555 μm), with the horizontal axis representing a vertical axis color difference value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis representing a normalized field angle. As can be seen from the figure, the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within +/-1.0 mu m, which shows that the optical lens can excellently correct chromatic aberration of an edge view field and a secondary spectrum of the whole image surface.

Fig. 4 shows an axial chromatic aberration diagram of example 1, which represents aberration of each wavelength on the optical axis at the imaging plane, the horizontal axis represents axial chromatic aberration value (unit: mm), and the vertical axis represents normalized pupil radius. As can be seen from the graph, the offset of the axial chromatic aberration is controlled within +/-0.08 mm, which indicates that the optical lens can better correct the axial chromatic aberration.

Fig. 5 shows a Modulation Transfer Function (MTF) graph of example 1, which represents imaging modulation degrees of different spatial frequencies at respective fields of view, with the horizontal axis representing spatial frequencies (units: lp/mm) and the vertical axis representing MTF values. As can be seen from the graph, the MTF values of the present embodiment are all above 0.5 in the full field of view, in the range of 0 to 150lp/mm, the MTF curve is uniformly and smoothly reduced in the process from the center to the edge field of view, and the present embodiment has good imaging quality and good detail resolution at both low frequency and high frequency.

Example 2

Referring to fig. 6, a schematic structural diagram of an optical lens provided in embodiment 2 of the present invention is shown, and the optical lens in this embodiment is substantially the same as the optical lens in embodiment 1 in terms of structural shape, and the main differences are that: the radius of curvature, center thickness, edge thickness, and material of each lens vary.

The relevant parameters of each lens in the optical lens in example 2 are shown in table 2.

TABLE 2

Fig. 7 to 10 show the optical distortion curve, the vertical axis chromatic aberration curve, the axial chromatic aberration curve, and the Modulation Transfer Function (MTF) curve of example 2, respectively. As can be seen from the figure, the optical distortion of the embodiment is controlled within ±8%, which indicates that the distortion of the optical lens is well corrected; the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within +/-1.0 mu m, which shows that the optical lens can excellently correct chromatic aberration of an edge view field and a secondary spectrum of the whole image surface; the offset of the axial chromatic aberration is controlled within +/-0.08 mm, which indicates that the optical lens can better correct the axial chromatic aberration; the MTF value of the embodiment is above 0.5 in the whole view field, and in the range of 0-150 lp/mm, the MTF curve is evenly and smoothly reduced in the process of viewing the field from the center to the edge, and the MTF has good imaging quality and good detail resolution under the conditions of low frequency and high frequency.

Example 3

Referring to fig. 11, a schematic structural diagram of an optical lens provided in embodiment 3 of the present invention is shown, and the optical lens in this embodiment is substantially the same as the optical lens in embodiment 1 in terms of structural shape, and the main differences are that: the radius of curvature, center thickness and edge thickness of each lens vary.

The relevant parameters of each lens in the optical lens in example 3 are shown in table 3.

TABLE 3 Table 3

Fig. 12 to 15 show an optical distortion curve, a homeotropic chromatic aberration curve, an axial chromatic aberration curve, and a Modulation Transfer Function (MTF) curve of example 3, respectively. As can be seen from the figure, the optical distortion of the embodiment is controlled within ±7%, which indicates that the distortion of the optical lens is well corrected; the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within +/-1.0 mu m, which shows that the optical lens can excellently correct chromatic aberration of an edge view field and a secondary spectrum of the whole image surface; the offset of the axial chromatic aberration is controlled within +/-0.07 mm, which indicates that the optical lens can better correct the axial chromatic aberration; the MTF value of the embodiment is above 0.46 in the whole view field, and in the range of 0-150 lp/mm, the MTF curve is evenly and smoothly reduced in the process of viewing the field from the center to the edge, and the MTF has good imaging quality and good detail resolution under the conditions of low frequency and high frequency.

Referring to table 4, the optical characteristics corresponding to the above embodiments include the effective focal length f, the maximum half field angle θ, the entrance pupil diameter EPD, the total optical length TTL, the aperture value FNO, the half image height IH, and the values corresponding to each of the conditional expressions in the embodiments.

TABLE 4 Table 4

Parameters and conditions	Example 1	Example 2	Example 3
				f(mm)	35.158	33.996	32.616
θ(°)	12.660	12.910	13.100
				EPD(mm)	10.045	9.713	9.319
TTL(mm)	49.049	48.540	50.306
				FNO	3.5	3.5	3.5
IH(mm)	8.1	8.1	8.1
				TTL/f	1.395	1.428	1.542
IH/f	0.230	0.238	0.248
				TTL/IH/θ	0.478	0.464	0.475
f123/f	0.845	0.887	1.018
				f2/f3	-1.308	-1.305	-1.266
CT2/CT3	3.439	3.483	3.574
				AT34/TTL	0.061	0.062	0.043
f45/f6	-4.731	-4.928	-9.556
				(CT4+CT5+AT56)/CT6	1.116	1.008	1.283
f7/f	0.717	0.750	0.799
				CT7/TTL	0.114	0.123	0.107
R1/f	0.577	0.598	0.671
				STL/TTL	0.801	0.782	0.758

In summary, according to the optical lens provided by the invention, the focal power of each lens is reasonably distributed, the surface of each lens is reasonably matched, the thickness of each lens and the distance between each lens are reasonably arranged, so that the optical lens has a field angle of more than 25 degrees, an optical total length of less than 51mm, optical distortion controlled within +/-8%, vertical axis chromatic aberration controlled within +/-1.0 mu m, axial chromatic aberration offset controlled within +/-0.08 mm, and MTF value controlled within a full field of view of more than 0.46, and the optical lens can realize high-pixel, small-distortion and miniaturized balance.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (10)

1. An optical lens, seven lenses altogether, characterized in that, from the object side to the imaging plane along the optical axis, are:

a first lens with positive focal power, wherein the object side surface of the first lens is a convex surface;

a second lens with positive focal power, wherein the object side surface of the second lens is a convex surface;

a third lens having negative optical power, an image side surface of the third lens being a concave surface;

a fourth lens with negative focal power, wherein the object side surface of the fourth lens is a concave surface;

a fifth lens having positive optical power, an image side surface of the fifth lens being a convex surface;

a sixth lens having negative optical power;

a seventh lens having positive optical power, an image side surface of the seventh lens being a convex surface.

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

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

4. The optical lens of claim 1, wherein an optical total 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: IH/f is more than 0.18 and less than 0.30.

6. The optical lens of claim 1, wherein an image height IH corresponding to the maximum half field angle of the optical lens and a maximum half field angle θ of the optical lens are satisfied by an optical total length TTL of the optical lens: TTL/IH/θ < 0.40 < 0.52.

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: 0.7 < f123/f < 1.2.

8. The optical lens of claim 1, wherein an air space AT34 between the third lens and the fourth lens on the optical axis and an optical total 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.