Optical lens
By designing the lens combination and aperture setting of negative and positive power in the security lens, the problems of low light throughput and poor picture clarity in the existing technology are solved, and the efficient imaging effect in low-light environments is achieved .
Patent Information
- Application Number
- CN202110072289.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-01-19
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2041-01-19
AI Technical Summary
Existing security lenses cannot clearly image when the light is dark, with low light passing and poor picture clarity, resulting in limited use effect.
An optical lens is designed, and seven sets of lenses are provided along the optical axis direction, including a combination of negative and positive power lenses. By reasonably allocating the light power and setting the aperture, the light-through diameter is increased and the picture clarity is improved.
It achieves good imaging effects in environments with weak light, increases the amount of light, improves the picture clarity, and achieves large aperture imaging.
Smart Images
Figure CN112731626B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of optical system design, and in particular to an optical lens. Background Art
[0002] At present, the development and application of security lenses are gradually expanding, and they are being used in various environmental conditions. In order to ensure good monitoring performance, the lens must have a high resolution to ensure the clarity of the monitoring image. Most existing security products are difficult to ensure a high degree of clarity, or they sacrifice a lot of light to achieve a certain resolution, which increases the difficulty of the software part in processing the brightness of the image, resulting in the lens being unable to clearly image in dim light conditions, and the use effect is limited. Summary of the invention
[0003] The main purpose of the present invention is to provide an optical lens, aiming to improve the technical problems of low light transmittance and poor picture clarity in the prior art.
[0004] To achieve the above object, the present invention provides an optical lens, the optical lens having an object side and an image side arranged opposite to each other along an optical axis direction, the optical lens comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an image plane arranged in sequence from the object side to the image side, wherein:
[0005] The first lens has negative optical power;
[0006] The second lens has negative optical power;
[0007] The third lens has positive optical power;
[0008] The fourth lens has positive refractive power;
[0009] The fifth lens has positive optical power;
[0010] The sixth lens has negative optical power;
[0011] The seventh lens has positive refractive power;
[0012] Wherein, the optical lens meets the following conditions: 0.95 <f / ENPD<1.05;
[0013] Wherein, f is the effective focal length of the optical lens, and ENPD is the entrance pupil diameter of the optical lens.
[0014] Optionally, the first lens is a biconcave lens, the second lens is a biconcave lens, the fourth lens is a biconvex lens, the fifth lens is a biconvex lens, the sixth lens is a biconcave lens, and the seventh lens is a biconvex lens.
[0015] Optionally, the optical lens satisfies the following conditions: -1.7 < f1 / f < -1.4, and -2.4 < f2 / f < -2.1, and 4.8 < f3 / f < 5.1, and 1.55 < f4 / f < 1.85, and 2.1 < f5 / f < 2.5, and -1.5 < f6 / f < -1.2, and 1.45 < f7 / f < 1.75;
[0016] Wherein, f is the effective focal length of the optical lens, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, and f7 is the effective focal length of the seventh lens.
[0017] Optionally, the optical lens satisfies the following conditions: 1.0 < R4 / R5 < 1.15;
[0018] Wherein, R4 is the radius of curvature of the image side surface of the second lens, and R5 is the radius of curvature of the object side surface of the third lens.
[0019] Optionally, the optical lens satisfies the following conditions: 0 < |Sag12 - Sag13| < 0.1;
[0020] Wherein, Sag12 is the distance between the highest point of the light ray on the image side surface of the sixth lens and the center of the lens on the optical axis, and Sag13 is the distance between the highest point of the light ray on the object side surface of the seventh lens and the center of the lens on the optical axis.
[0021] Optionally, the optical lens satisfies the following conditions: 1.5 < TH / f < 2.0;
[0022] Wherein, TH is the diameter of the image plane, and f is the effective focal length of the optical lens.
[0023] Optionally, the optical lens further includes a diaphragm, and the diaphragm is disposed between the third lens and the fourth lens.
[0024] Optionally, the optical lens satisfies the following conditions: 0.33 < T1 / T2 < 0.43;
[0025] Wherein, T1 is the distance from the object side surface of the first lens to the diaphragm on the optical axis, and T2 is the distance from the diaphragm to the image plane on the optical axis.
[0026] Optionally, the first lens is a spherical glass lens, the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are all aspherical plastic lenses, and the fourth lens is an aspherical glass lens.
[0027] Optionally, the optical lens further includes an infrared filter, and the infrared filter is disposed between the seventh lens and the image plane.
[0028] In the technical solution provided by the present invention, the optical lens is provided with a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, a seventh lens with positive optical power and an image plane in sequence from the object side to the image side. Light carrying information of the photographed object can pass through the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens in sequence and finally form an image on the image plane. Through the reasonable arrangement of the seven groups of lenses, the optical lens has good optical performance, and the ratio of the effective focal length of the optical lens to the entrance pupil diameter of the optical lens is between 0.95 and 1.05, which is conducive to increasing the light aperture of the optical lens, thereby increasing the light throughput, improving the picture clarity, and achieving the effect of large aperture imaging. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.
[0030] Figure 1 A schematic structural diagram of an embodiment of an optical lens provided by the present invention;
[0031] Figure 2 for Figure 1 Schematic diagram of the MTF curve of the optical lens in the high frequency band at room temperature;
[0032] Figure 3 for Figure 1 Schematic diagram of the MTF curve of the optical lens in the low frequency band at room temperature.
[0033] Description of Figure Numbers:
[0034]
[0035] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0037] It should be noted that if a directional indication is involved in the embodiment of the present invention, the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.
[0038] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.
[0039] At present, the development and application of security lenses are gradually expanding, and they are being used in various environmental conditions. In order to ensure good monitoring performance, the lens must have a high resolution to ensure the clarity of the monitoring image. Most existing security products are difficult to ensure a high degree of clarity, or they sacrifice a lot of light to achieve a certain resolution, which increases the difficulty of the software part in processing the brightness of the image, resulting in the lens being unable to clearly image in dim light conditions, and the use effect is limited.
[0040] In view of this, the present invention provides an optical lens, which aims to improve the technical problems of low light transmittance and poor image clarity in the prior art. Figures 1 to 3 This is an embodiment of the optical lens.
[0041] First of all, it should be explained that the focal power characterizes the ability of an optical system to deflect light. The focal power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam. When the focal power is a positive number, the refraction of light is convergent; when the focal power is a negative number, the refraction of light is divergent. The larger the absolute value of the focal power, the stronger the ability to bend light, and the smaller the absolute value of the focal power, the weaker the ability to bend light. The focal power can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (i.e., a lens group).
[0042] The optical lens has an object side and an image side which are arranged opposite to each other along the optical axis direction, and the optical lens comprises a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7 and an image plane 10 which are arranged in sequence from the object side to the image side, wherein the first lens 1 has a negative optical power, the second lens 2 has a negative optical power, the third lens 3 has a positive optical power, the fourth lens 4 has a positive optical power, the fifth lens 5 has a positive optical power, the sixth lens 6 has a negative optical power, and the seventh lens 7 has a positive optical power;
[0043] And wherein, the optical lens meets the following conditions: 0.95 <f / ENPD<1.05;
[0044] Wherein, f is the effective focal length of the optical lens, and ENPD is the entrance pupil diameter of the optical lens.
[0045] In the technical solution provided by the present invention, the image plane 10 can be understood as the surface of the image sensor, and the light carrying the information of the object can pass through the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 in sequence and finally form an image on the image plane 10. Through the reasonable arrangement of the seven groups of lenses, the optical lens has good optical performance, and the ratio of the effective focal length of the optical lens to the entrance pupil diameter of the optical lens is between 0.95 and 1.05, which is conducive to increasing the light aperture of the optical lens, thereby increasing the light throughput, improving the picture clarity, and achieving the effect of large aperture imaging.
[0046] Specifically, in this embodiment, in order to make the first lens 1 have a negative optical power, the second lens 2 have a negative optical power, the third lens 3 have a positive optical power, the fourth lens 4 have a positive optical power, the fifth lens 5 have a positive optical power, the sixth lens 6 have a negative optical power, and the seventh lens 7 have a positive optical power, the first lens 1 is a biconcave lens, the second lens 2 is a biconcave lens, the third lens is a biconvex lens, the fourth lens 4 is a biconvex lens, the fifth lens 5 is a biconvex lens, the sixth lens 6 is a biconcave lens, and the seventh lens 7 is a biconvex lens.
[0047] Specifically, in this embodiment, the optical lens satisfies the following conditions: -1.7 < f1 / f < -1.4, and -2.4 < f2 / f < -2.1, and 4.8 < f3 / f < 5.1, and 1.55 < f4 / f < 1.85, and 2.1 < f5 / f < 2.5, and -1.5 < f6 / f < -1.2 and 1.45 < f7 / f < 1.75; where f is the effective focal length of the optical lens, f1 is the effective focal length of the first lens 1, f2 is the effective focal length of the second lens 2, f3 is the effective focal length of the third lens 3, f4 is the effective focal length of the fourth lens 4, f5 is the effective focal length of the fifth lens 5, f6 is the effective focal length of the sixth lens 6, and f7 is the effective focal length of the seventh lens 7. By controlling the effective focal lengths of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7, the optical power of the optical lens is reasonably distributed, so that the chromatic aberration between the lenses compensates for each other, and when the entrance pupil diameter increases, it can also ensure high color reproducibility, so that the optical lens can still have a good imaging effect even in a weak light environment.
[0048] Specifically, in this embodiment, the optical lens satisfies the following conditions: 1.0 < R4 / R5 < 1.15; where R4 is the radius of curvature of the image side of the second lens 2, and R5 is the radius of curvature of the object side of the third lens 3.
[0049] Specifically, in this embodiment, the optical lens satisfies the following conditions: 0 < |Sag12 - Sag13| < 0.1; where Sag12 is the distance between the highest point of the image side light ray of the sixth lens 6 and the lens center on the optical axis, and Sag13 is the distance between the highest point of the object side light ray of the seventh lens 7 and the lens center on the optical axis. When the above conditions are met, the large-angle deflection of the incident light on the surface of the seventh lens 7 can be effectively controlled, which helps to reduce the tolerance sensitivity, reduce the processing difficulty, improve the production yield, and can avoid the appearance of serious ghost images, providing a basic condition for the large aperture performance.
[0050] Specifically, in this embodiment, the optical lens satisfies the following condition: 1.5 < TH / f < 2.0; where TH is the diameter of the image plane 10, and f is the effective focal length of the optical lens. When the above conditions are met, it can ensure that the optical lens has a large field of view and that light at large angles can also reach the image plane 10.
[0051] Specifically, the optical lens further includes a diaphragm 8, which is disposed between the third lens 3 and the fourth lens 4. The diaphragm 8 is used to limit the light beam to further improve the imaging quality of the optical lens. When the diaphragm 8 is disposed between the third lens 3 and the fourth lens 4, it can effectively converge the light entering the optical lens and reduce the aperture of the lenses in the optical lens. In this embodiment, the diaphragm 8 can be an aperture stop. By disposing a fourth lens 4 with a positive focal power after the aperture stop, it can further correct the aberration generated by the front lens group and at the same time make the light beam converge again, which can increase the aperture of the lens and shorten the overall length of the lens, making the optical lens more compact and having a relatively short overall length.
[0052] Specifically, in this embodiment, the optical lens satisfies the following condition: 0.33 < T1 / T2 < 0.43; where T1 is the distance from the object side surface of the first lens 1 to the diaphragm 8 on the optical axis, and T2 is the distance from the diaphragm 8 to the image plane 10 on the optical axis. When the above conditions are met, it can ensure that the front and rear light heights are within a certain range, ensure that the light aperture in the object side direction can meet the structural requirements, control the volume within a certain range, and avoid the situation where light cannot reach the edge of the picture and present vignetting.
[0053] Specifically, in this embodiment, the first lens 1 is a spherical glass lens, the second lens 2, the third lens 3, the fifth lens 5, the sixth lens 6, and the seventh lens 7 are all aspherical plastic lenses, and the fourth lens 4 is an aspherical glass lens. The characteristics of aspherical lenses are that the curvature changes continuously from the center to the periphery of the lens. Different from spherical lenses with a constant curvature from the center to the periphery of the lens, aspherical lenses have better curvature radius characteristics and have the advantages of improving distortion aberration and astigmatism aberration. After using aspherical lenses, it can eliminate the aberration that appears during imaging as much as possible, thereby improving the imaging quality of the lens.
[0054] In this embodiment, the first lens 1 and the fourth lens 4 are made of glass, which can reduce the influence of temperature on the optical performance of the lens; the second lens 2, the third lens 3, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are all made of plastic, which can reduce the weight of the optical lens and reduce the cost.
[0055] Specifically, in this embodiment, the optical lens also includes an infrared filter 9, which is arranged between the seventh lens 7 and the image plane 10. By setting the infrared filter 9, the optical lens can filter out infrared light to prevent infrared light from reaching the image sensor and interfering with normal visible light imaging, thereby improving imaging quality.
[0056] Furthermore, the optical lens may further include a protective glass, which is disposed between the infrared filter 9 and the image plane 10 to prevent internal components (eg, chips) of the optical lens from being damaged.
[0057] It can be understood that the light carrying the information of the subject can pass through the first lens 1, the second lens 2, the third lens 3, the aperture 8, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the infrared filter 9, the protective glass in sequence and finally form an image on the image plane 10.
[0058] In this embodiment, each lens has an object side surface and an image side surface, which are respectively the object side surface S1 of the first lens, the image side surface S2 of the first lens, the object side surface S3 of the second lens, the image side surface S4 of the second lens, the object side surface S5 of the third lens, the image side surface S6 of the third lens, the object side surface S7 of the fourth lens, the image side surface S8 of the fourth lens, the object side surface S9 of the fifth lens, the image side surface S10 of the fifth lens, the object side surface S11 of the sixth lens, the image side surface S12 of the sixth lens, the object side surface S13 of the seventh lens, and the image side surface S14 of the seventh lens. The aperture is ST, the object side surface of the infrared filter is S15, and the image side surface of the infrared filter is S16.
[0059] Specifically, in this embodiment, the parameters of the optical lens are shown in the following table.
[0060] Table 1 Parameters of the optical lens
[0061]
[0062] It can be seen from Table 1 that the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are all aspherical lenses. In this embodiment, the surface shape Z of each aspherical lens can be defined by but not limited to the following aspherical formula:
[0063]
[0064] Among them, Z is the distance vector height from the vertex of the aspherical surface when the aspherical surface is at a height of h along the optical axis, c is the paraxial curvature of the aspherical surface, c=1 / R (that is, the paraxial curvature c is the inverse of the curvature radius in the above table), K is the cone coefficient, , , , , , , , is the coefficient corresponding to the high-order term. The high-order coefficients of each aspherical mirror surface can be seen from Table 2 and Table 3 below.
[0065] In this embodiment, the following Tables 2 and 3 give the high-order coefficients of each aspherical mirror surface.
[0066] Table 2 High-order coefficients of the aspherical surfaces of the second lens, the third lens, and the fourth lens
[0067]
[0068] Table 3 High-order coefficients of the aspherical surfaces of the fifth lens, the sixth lens, and the seventh lens
[0069]
[0070] Among them, E-01 represents 10 to the power of -1, E-02 represents 10 to the power of -2, and so on. EN represents 10 to the power of -N.
[0071] Specifically, in this embodiment, Figure 2 This is a schematic diagram of the MTF curve of the high frequency band of the optical lens provided by the present invention at room temperature, that is, a schematic diagram of the MTF curve in the spatial frequency range between 0-250.
[0072] Figure 3 This is a schematic diagram of the MTF curve of the optical lens provided by the present invention in the low frequency band at room temperature, that is, a schematic diagram of the MTF curve with a spatial frequency between 0-125.
[0073] And from the above two figures, we can see that the MTF of 250lp-mm within 0.8F of the center and the periphery is above 0.15, and the MTF of 125lp-mm is above 0.4, which can match the chip with 2um pixel size and ensure better imaging effect.
[0074] The optical lens achieves miniaturization by ensuring that the total length of the lens is less than 23 mm through reasonable selection of lens materials, optimization of lens shapes, and reasonable distribution of optical power, and makes the maximum optical distortion of the optical lens less than -40%. The optical lens F number reaches 1.0 to ensure the brightness of the picture, and the optical lens increases the light aperture, thereby increasing the amount of light passing through and achieving a large aperture imaging effect.
[0075] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.
Claims
1. An optical lens, characterized in that: The optical lens has an object side and an image side which are arranged opposite to each other along the optical axis direction, and the optical lens is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an image plane which are arranged in sequence from the object side to the image side, wherein: The first lens has negative optical power; The second lens has negative optical power; The third lens has positive optical power; The fourth lens has positive refractive power; The fifth lens has positive optical power; The sixth lens has negative optical power; The seventh lens has positive optical power; Wherein, the optical lens meets the following conditions: 0.95 <f / ENPD<1.05; Wherein, f is the effective focal length of the optical lens, and ENPD is the entrance pupil diameter of the optical lens; The optical lens satisfies the following conditions: -1.7< f1 / f<-1.4, and -2.4< f2 / f <-2.1, and 4.8< f3 / f <5.1, and 1.55< f4 / f <1.85, and 2.1< f5 / f <2.5, and -1.5< f6 / f <-1.2, and 1.45< f7 / f <1.75; Wherein, f is the effective focal length of the optical lens, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, and f7 is the effective focal length of the seventh lens; The first lens is a biconcave lens, the second lens is a biconcave lens, the fourth lens is a biconvex lens, the fifth lens is a biconvex lens, the sixth lens is a biconcave lens, and the seventh lens is a biconvex lens.
2. The optical lens according to claim 1, wherein: The optical lens meets the following conditions: 1.0< R4 / R5<1.15; Wherein, R4 is the curvature radius of the image side surface of the second lens, and R5 is the curvature radius of the object side surface of the third lens.
3. The optical lens according to claim 1, wherein: The optical lens satisfies the following conditions: 0<|Sag12-Sag13| <0.1; Among them, Sag12 is the distance between the highest point of the image side light of the sixth lens and the center of the lens on the optical axis, and Sag13 is the distance between the highest point of the object side light of the seventh lens and the center of the lens on the optical axis.
4. The optical lens according to claim 1, wherein: The optical lens meets the following conditions: 1.5 <TH / f<2.0; Wherein, TH is the diameter of the image plane, and f is the effective focal length of the optical lens.
5. The optical lens according to claim 1, wherein: The optical lens further includes a stop, and the stop is disposed between the third lens and the fourth lens.
6. The optical lens according to claim 5, characterized in that: The optical lens meets the following conditions: 0.33 <T1 / T2<0.43; Wherein, T1 is the distance from the object side surface of the first lens to the aperture on the optical axis, and T2 is the distance from the aperture to the image plane on the optical axis.
7. The optical lens according to claim 1, wherein: The first lens is a spherical glass lens, the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are all aspherical plastic lenses, and the fourth lens is an aspherical glass lens.
8. The optical lens according to claim 1, wherein: The optical lens further includes an infrared filter, and the infrared filter is arranged between the seventh lens and the image plane.